How to know if a real-time classifier is achivable in a low-power emdedded system?
Regarding your first point, it depends on what neural network you would like to use, the sensor temporal resolution, and the capabilities of the embedded system. You can figure out the number of operations required for a forward pass of your network, then when combined with the internal clock of the embedded system, you can calculate the approximate time it would take for one classification event in real time.
A good explanation is given here
What is the computational complexity of the forward pass of a convolutional neural network?
If you have the computational complexity of your network, and the number of CPU cycles per seconds, you can roughly approximate the time.